Oxidation/ammoxidation catalyst

ABSTRACT

An oxidation/ammoxidation catalyst contains the elements antimony, uranium, iron and bismuth in a catalytic active oxidized state.

United States Patent [1 Li et al.

[ 1 Dec.9, 1975 [52] US. Cl 252/456; 252/470 [51] Int. C1. B01] 29/16; B011 29/26;

B01J 23/64; B01J 23/84 [58] Field of Search 252/456, 470

[56] References Cited UNITED STATES PATENTS 3,328,315 6/1967 Callahan et a1 H 252/470 X 3,338,952 8/1967 Callahan et a1.... a 252/470 X 3,431,292 3/1969 Callahan et al.... 252/456 X 3,445,521 5/1969 Callahan et a1 r 4, 252/456 X 3,542,842 11/1970 Grasselli et al. i 252/456 X 3,625,867 12/1971 Yoshino et a1 .4 252/456 3,636,066 1/1972 Yamada et a1 252/470 X 3,657,155 4/1972 Yoshino et a1 252/456 Primary ExaminerPau1 F. Shaver Attorney, Agent, or Firm-Paul L. Passley [57] ABSTRACT An oxidation/ammoxidation catalyst contains the elements antimony, uranium, iron and bismuth in a catalytic active oxidized state.

4 Claims, N0 Drawings OXIDATION/AMMOXIDATION CATALYST BACKGROUND OF THE INVENTION This invention relates to an improved oxidation andlor ammoxidation catalyst system containing the elements antimony, uranium, iron and bismuth and to a method for preparing such catalyst system.

It is well known that olefins can be oxidized to oxygenated hydrocarbons such as unsaturated aldehydes and acids, for example, acrolein and methacrolein, acrylic and methacrylic acid. It is also well known that olefins can be ammoxidized to unsaturated nitriles such as acrylonitrile and methacrylonitrile. The value of such oxygenated hydrocarbons and unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.

Various catalytic processes are known for the oxidation and/or ammoxidation of olefins. Such processes commonly react an olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant and for the production of methacrolein and methacrylonitrile, isobutylene is the generally used olefiin reactant.

A catalyst system composed of the oxides of antimony and uranium and the oxidation and ammoxidation of olefins using such catalyst has been described in [1.8. Letters Pat. Nos. 3,198,750 and 3,308,151. These patents describe preparation of the catalyst by precipitation wherein the oxides of the elements are contained in a slurry which is filtered to remove soluble salts and recover the catalytic components as the filter cake.

In the catalytic oxidation and/or ammoxidation of olefins, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the conversion of the olefin and the yield of the desired product. In many cases a reduction in the cost of a catalyst system in the order of a few pennies per pound or a 1% increase in the yield of a desired product represents a tremendous commercial economical savings. Accordingly, research efforts are continuously being made to define new or improved catalyst systems and methods of making new and old catalyst systems to reduce the cost and/or to upgrade the activity and selectivity of such catalyst systems in particular processes.

SUM MARY This invention is directed to an improved catalyst system containing the elements antimony, uranium, iron and bismuth having commercial activity and selectivity for the catalytic oxidation and/or ammoxidation of olefins and to an improved method of making such catalyst system.

Accordingly, typical objects of this invention are to provide: (1) an improved oxidation and/or ammoxidat| on catalyst system containing oxygen, antimony, uramum, iron and bismuth, (2) an improved process for the preparation of a catalyst system containing oxygen, antimony, uranium, iron and bismuth, and (3) an improved olefin conversion process.

Other objects, aspects and advantages of this invention will become apparent to those skilled in the art upon further study of this disclosure and the appended claims.

2 In accordance with this invention, a new oxidationlammoxidation catalyst system based on the elements antimony, uranium, iron and bismuth is provided. The elements are in combination with oxygen and may exist as individual oxides or as complexes of two or more of the elements and oxygen as a combination of oxides and complexes. The atomic ratio of the elements present in the catalyst system may vary over a wide range. Generally speaking the catalyst may be defined by the following empirical formula:

sb U Fe Bi o wherein a is 1 10, b is 0.01 to l, c is 0.01 to 1, d is 0.001 to 0.1 and e is a number taken to satisfy the average valences of the Sb, U, Fe and Bi in the oxidation states in which they exist in the catalyst.

The catalyst can be prepared starting with individual oxides or sulfates of the elements. A preferred method of preparing the catalyst is to combine the oxides or sulfates of the elements with sulfuric acid. When antimony sulfate is used as a starting material, it can be added to water wherein sulfuric acid is obtained. Nitric acid is used to oxidize the sulfate salts of the elements or to further oxidize the oxides of the elements. After the acid mixture has digested, the pH of the mixture is adjusted to about 8 followed by filtration.

After filtering the mixture, the filter cake can be dried at a temperature of from about C to about 180C. A suitable drying temperature is about C. However, the drying can be obtained at higher temperatures such as up to about 650C. The time required for drying the filter cake can range from an hour up to about 64 hours. Obviously, the drying temperature selected will dictate the required drying time with the lower temperature requiring the longer time. Also, the filter cake may be dried at different temperatures, for example at l 10C for from 2 to 64 hours and then at a temperature of from about 250C to about 650C for from 2 to 24 hours.

After the filter cake is dried, it is further heated at an elevated temperature to obtain the active catalytic form of the elements. This calcination of the catalyst is conducted at a temperature in the range of from about 500C to about lC. The time for calcination can vary and depends upon the temperatures employed. Generally, a time period of 2 to 24 hours at the designated temperatures is sufficient. The calcination may be conducted in the presence of oxygen (air); however, the catalyst may also be made active by calcining it in the absence of oxygen, such as in a nitrogen atmosphere.

The catalyst can be employed without support, and will display excellent activity. It also can be combined with a support, and preferably at least 5% up to about 90% preferably 5 to 50%, of the supporting compound by weight of the entire composition is employed in this event. Any known support materials can be used, such, for example, silica, alumina, zirconia, alundum, silicon carbide, alumina-silica, and the inorganic phosphates, silicates, aluminates, borates and carbonates stable under the reaction conditions to be encountered in the use of the catalyst.

The improved catalyst of this invention exhibits exceptional utility in the conversion of olefins with or without the presence of ammonia. The olefins employed as reactants for conversion by the catalyst of this invention may be open chain as well as cyclic and include, for example, propylene, butene-l, butene-2, isobutene, pentene-l, pentene-2, 3-methyl butene-l,

2-methy1 butene-2, hexene-l, hexene-2, 4-methyl pentene-l, 3,3 dimethyl butene-l 4-methyl pentene-2, oc-

% propylene (C H converted tene-l, cyclopentene, cyclohexene, and the like. Particularly, when the catalyst of this invention is used as merely an oxidation catalyst, it is particularly adapted to PmPYlene acrylonlmle mols C,H, in feed to the conversion of propylene to acrolein and isobutylene to methacrolein. Of course, mixtures of olefins may be employed and mixtures of olefins with other hydrocarbons are applicable to the process of this invention.

When the catalyst of this invention is to be used as an 0.5:1 to 5:1 and preferably slightly over the stoichio metric ratio of 1:1 ammoniazolefin will be employed.

While ammonia is most generally employed as the nitrogen providing compound, other nitrogen containing materials may be employed which decompose to produce reactive nitrogen under the reaction conditions.

Any source of oxygen, pure or in admixture with inerts, may be employed in the process of this invention. Air is a satisfactory source of oxygen for use in this invention.

The catalyst system of this invention can be advantageously employed for synthesizing styrene from ethylbenzene and oxygen, butadiene from butenes and oxygen, acrolein or methacrolein from propylene or isobutylene and oxygen, acrylonitrile or methacrylonitrile from propylene or isobutylene, ammonia and oxygen,

isoprene from 2-methyl butene-Z and oxygen, and 2- cyano-l,3-butadiene from Z-methyl butene-2 or isoprene, ammonia and oxygen.

DESCRIPTION OF PREFERRED EMBODIMENTS The following Examples are presented as illustrative of the invention and, as such, are not intended to be restrictive upon the specific materials, quantities and operation variables specifically set forth therein.

As used in the examples, the following terms have the following definitions:

mols C H in feed mols C 14,, in effluent mols AN formed The apparatus employed in carrying out the runs in this example is a fluidized bed type reactor. The reactor consists of a 14 mm. inside diameter 96% quartz glass tube fitted at the bottom with a fritted disc for supporting a catalyst bed of up to ml. in volume and fitted at the top with another fritted disc to remove entrained catalyst from the reactor efiluent. A thermowell of 4 mm. outside diameter 96% quartz glass extends through the center of the catalyst bed to the fritted disc. The reactor tube is jacketed with a larger tube in which sand is fluidized for providing even heat distribution. The entire reactor assembly is placed in a controlled, hinged tube furnace. The reactant gases are premixed and heated to about 470C before entering the bottom of the reactor through a single inlet tube. The effluent gases from the reactor are heated to prevent condensation prior to chromatographic analysis.

EXAMPLE 1 Five catalyst systems composed of antimony, uranium, iron and bismuth are prepared by adding antimony, uranium and bismuth oxides and iron sulfate to 290 ml. of water to which is then added 83 grams of 98% H 50 The mixture is stirred for about 3 hours at a temperature of C. Nitric acid is added to the mixture which is then stirred for 2 hours to further oxidize the elements. After cooling the mixture the pH is adjusted to about 8 with ammonium hydroxide. The mixture is allowed to digest about 16 hours. After digestion the mixture is filtered and the precipitate is washed with water. The precipitate is mixed with silica sol (Ludox AS) and the mixture is evaporated to dryness and further dried at about C for about 16 hours. The resulting catalyst is calcined at 500C for 1 hour, then at 700C for 1 hour and then at 900C for 12 hours. The quantities of the various components used in making catalyst systems are given in the following Table 1.

TABLE l-continued COMPONENT CATA CAT.B CAT.C CATD CAT.E

EXAMPLE II TABLE lll-continued Three catalyst systems made according to the general Catalyst A B procedure of Example 1 are used in the conversion of 10 Feed Flow Rate (ml/sec.) at STP propylene and ammonia to acrylonitrile using the appazz previously i g' 2 feed 'g g m The above example shows that various atomic ratios of ese comparatwe runs m propy' antimony in the catalyst system of this invention are lene, 17.5% oxygen and 65.1% helium. In each run the useful temperature is about 490C and the pressure is varied.

Other process data and the results are given in Table ll. EXAMPLE W g g gga ig The catalyst systems of Example I are used in the 3- F 0 conversion of isobutylene to methacrylonitrile using 30% the apparatus previously described. Methacrylonitrile l 2 is obtained using each catalyst with a feed composition TABLE 1] Catalyst A B C Catalyst Weight (grams) 30 30 30 30 30 Pressure (psig) 0.6 l8 1 l8.2 l 18 Contact Time (grnsee/ml.) at $1? 5 s 6 6 6 6 Elapsed Reaction (min) 65 21s 35 15s 65 185 Percent Propylene Converted 88.9 94.9 92.9 95.9 90.4 94.8

Percent Propylene to Acrylonitrile 7L3 65.6 78.9 739 N3 66.9 Stability s u s s s s S Stable U Unstable reaction temperature of 465C Weight of Catalyst (grams) Contact time determined as Feed How Rate (nu/sea) at The above example shows the improved ammoxidation activity of the four component catalyst system of this invention compared with three component catalysts of 8.9% ammonia, 8.5% isobutylene, 17.5% oxygen and and the stability and the improvement of acrylonitrile 65.1% helium, all on a volume basis, at a temperature yield of the four component system under pressure opof 500C and atmospheric pressure.

eration.

EXAMPLE V EXAMPLE The catalyst systems of Example 1 are used in the Two catalyst systems made according to the general conversion of propylene to acrolein using the apparatus procedure of Example I are used in the conversion of previously described. Acrolein is obtained using each propylene and ammonia to acrylonitrile using the appacatalyst with a feed composition of 7.0% propylene, ratus previously described. The feed composition in l 1% oxygen and 82% helium, all on a volume basis, at

these comparative runs is 8.9% ammonia, 8.5% propya temperature of 500C and atmospheric pressure. lene, 17.5% oxygen and 65.1% helium. In each run the From the foregoing example it will be clearly noted temperature is about 490C, 30.0 grams of catalyst is that the catalyst system of this invention exhibits activused and the contact time is 6 gm.sec./ml (at STP). ity, selectivity and stability whhen used at elevated Other process data and the results are given in Table pressures.

Ill. The catalysts are identified as: It will be obvious to persons skilled in the art that var- A. Sb, U ,Fe Bi 30% SD: ious modifications may be made in the improved cata- B. Sb U Fe Bi 25% SiO, lyst and process as described in this application. Ac-

cordingly, it is intended that all such modifications TABLE ll] which reasonably fall within the scope of the appended A 3 claims are a part hereof.

Pressure (psig) 18.5 1 18.5 What is claimed is:

Percent Pro Iene convened P 89.9 95. l 868 929 l. A catalyst system suitable for operation under Percent Propylene pressure comprising the elements antimony, uranium,

to Acrykmilrile iron and bismuth m an oxidized state represented by Weight of Catalyst (grams) the formula:

Sb U Fe Bi O mixture at a temperature of from about 500C to about 1 C to form said active oxidation states.

2. The catalyst system of claim 1 wherein said mixture is formed from Sb O U 0 Bi 0 and FeSOfi- H 0.

3. The catalyst system of claim 1 wherein said mixture is oxidized with nitric acid prior to the pH adjustment.

4. The catalyst system of claim 1 wherein the support is silica. 

1. A CATALYST SYSTEM SUITABLE FOR OPERATION UNDER PRESSURE COMPRISING THE ELEMENTS ANTIMONY,URANIUM, IRON AND BISMUTH IN AN OXIDIZED STATE REPRESENTED BY THE FORMULA
 2. The catalyst system of claim 1 wherein said mixture is formed from Sb2O3, U3O8, Bi2O3 and FeSO4.7H2O.
 3. The catalyst system of claim 1 wherein said mixture is oxidized with nitric acid prior to the pH adjustment.
 4. The catalyst system of claim 1 wherein the support is silica. 